I'm pretty new to this, so forgive me if I get some things wrong. I am working with a piece of equipment that uses an Arduino Pro Mini. When I first got to it, I realized that some of the code was incorrect and wanted to fix it. Unfortunately, my Pro Mini is soldered into the board with the labels and pins down, so the only accessible pins are the top six, and even those aren't labeled. The reset button is also upside down. I tried using a FT232H FTDI hooked up (using a pinout because of the aforementioned no labels)

D0-> TX

D1-> RX

which I was told should work, but when I plug in the micro-usb into the FT232H and try to upload the sketch, it gives me the error

avrdude: stk500_getsync(): not in sync: resp=0x00

and also blinks green but has a constant red light (from what I can see from looking under the board). Because this Pro Mini controls my equipment, I'm wary of doing anything too intense. Any ideas of how to fix this without breaking my apparatus?

Update! I changed the pinning, and the IDE told me that it uploaded, but it still won't run the program! Help!

  • An FTDI breakout should use more than two pins, check the Pro Mini datasheet for the correct pins to connect through a breakout. You might also benefit from looking up an Arduino FTDI tutorial on YouTube. Just make sure to check the simple things first :)
    – fewr
    Jun 15, 2017 at 18:25
  • 2
    Please edit your question to include a list of exactly which pins you can connect to. “The top six” is too vague. Eg, are the ISP pins accessible? Also please edit your question to make a list of unused pins Jun 15, 2017 at 18:46
  • If you want to know which pins are which, Google search for "arduino pro mini pinout diagram". You will find lots of them.
    – KC Tucker
    Jun 15, 2017 at 20:11
  • "IDE told me that it uploaded, but it still won't run the program". It's likely the problem is with your code. Try uploading a minimal known-working sketch to see if it will run. The obvious choice would be File > Examples > 01.Basics > Blink but first you should make sure that the pin being blinked (13 by default) won't have any harmful effect on your equipment.
    – per1234
    Jun 16, 2017 at 6:57
  • On some pro-minis, such as the one I got off Amazon, the FTDI header pins are mirrored. You may not be able to go by a downloaded pinout diagram without verifying the pins. Feb 20, 2023 at 9:01

1 Answer 1


Same problem faced. Try out many times with proper connection but no success. After that, I found one unique and simple solution. I use Arduino Uno instead of FTDI. Follow below step, your problem will definitely solve.

  1. First, remove Arduino Uno's IC means ATMEGA 328P-PU.
  2. Now, do connection as shown in below figure.

Uno Connect with Pro mini

Connections are like:

Arduino Uno(Without Chip)     Arduino Mini Pro

          RX                         RX
          TX                         TX
          +5V                        Vcc
          GND                        GND
         RESET                  RST(RESET PIN)
  1. Now, plug your Arduino Uno to your computer and open your Arduino IDE.

  2. Now, an open sketch which one you want to upload. Now, go to Tools and select board in which you want to upload code. Below, show in the figure.

Select your board

  1. Now, upload your program. It will definitely work.

I hope it will help you.

  • Could you possibly provide a reference link to some relevant documentation that explains this type of configuration please?
    – stevieb
    Jun 16, 2017 at 14:57
  • This should not be necessary. Uploading via an FTDI does work. Jun 16, 2017 at 16:22
  • @stevieb There is no proper documentation about this but I read out this thing in the forum. Prefer this link stackoverflow.com/questions/18362942/…
    – Hasan
    Jun 17, 2017 at 6:17
  • @ChrisStratton But FTDI not worked for me. That's why I found out this solution.
    – Hasan
    Jun 17, 2017 at 6:21
  • Then you did not use the FTDI correctly. It will work for someone who does. Postings here are not only for the benefit of the asker, but for that of future readers too. Using an Arduino as a serial adapter is a possibility, but the traditional method of using an FTDI is a fine solution too, if that is what is on hand. Jun 17, 2017 at 13:49

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